1. Field of the Invention
The present invention relates to laser diodes, and in particular to a laser diode mounted on a heat sink having a strip-shaped radiation-emitting zone.
2. Description of the Prior Art
Laser diodes are known in the art (Electronic Letters Vol. 18 (1982) pp. 629, FIG. 2) which are coupled to a glass fiber or light wave guide serving for radiation transmission. Such conventional laser diodes are soldered onto a heat sink. For this purpose, conventional heat sinks generally have a V-shaped groove above which the laser diode, in the form of a semiconductor chip, is situated. The V-shaped groove functions to accept the solder, and is filled to its upper level with solder. As seen by the chip, the body of the heat sink and the solder disposed in the groove form a substantially smooth surface on which the chip is located. This groove, which typically has a width of approximately 75 micrometers, and the laser diode chip situated thereabove are aligned relative to each other such that the groove and the radiation-emitting, or laser-active, zone of the chip are above one another. The surface of the body of the heat sink has further grooves running at right angles to this groove, which are provided as a means for solder flow.
As is known, a laser diode emits laser radiation through an end face of a chip having a strip-shaped laser-active zone. For employment of the laser diode in combination with a light conducting fiber, the chip and the fiber are aligned relative to each other such that the end face of the chip and the end face of the fiber are opposite each other up to a spacing of approximately 20 micrometers, with the center axis of the fiber being adjusted to the radiation-generating center of the strip-shaped laser-active zone of the chip.
One possibility for mounting the laser diode (that is, the chip in which the laser diode is realized) on the heat sink is known as an upside-down arrangement. This means that the laser-active zone is situated in the semiconductor chip very close to the surface of the chip which is adjacent to the heat sink, for example, at a distance of only two through five micrometers. The laser-active zone is generally disposed in one of a plurality of epitaxial layers which are applied to a semiconductor body, the semiconductor body being significantly thicker in comparison to these layers. The position of the laser diode must thereby be adjusted within a precision range of .+-.2 micrometers so as not to generate any disruptive side effects in the beam propagation. Achieving such precise adjustment is a problem in the assembly of such laser diodes.